Hydrodynamic characteristics and effects of river waves caused by ice jam releases

摘要

Ice-jam release waves, or javes for short, are highly dynamic events that occur in ice-forming rivers. They are known for serious ecological and socio-economic impacts, which are usually detrimental but on occasion beneficial, particularly with respect to ecosystem maintenance in the large freshwater deltas of northern Canada. Detailed water level data have been obtained during the passage of javes in the past 10 years or so, but their study is hampered by lack of velocity and discharge measurements, owing to the presence of moving ice in the flow. A previously developed method to analytically compute such parameters, which is based on measured waveforms, has given encouraging results in several applications. Herein, this method is first subjected to comprehensive validation using numerical model output for a hypothetical jave in a prismatic channel. The analytical method is shown to perform adequately with respect to all hydrodynamic jave characteristics, such as celerity, velocity, discharge, and bed shear stress. Jave data from various rivers are then compiled in tabular form and it is shown via dimensional analysis that bulk predictions can be made in terms of jave height and rate of rise of the water level. Implications of the present findings to riverbed scour and to ecologically vital ice-jam flooding of flat rivers and deltas are explored and research challenges identified.